The invention relates to a high-pressure discharge lamp comprising an elongate discharge vessel which is sealed in a vacuumtight manner, has a wall of ceramic material, and is provided with an ionizable filling and with a first and a second electrode which are arranged at respective ends of the discharge vessel and which are each connected to a respective current supply conductor which issues through the wall of the discharge vessel to the exterior, which discharge vessel is provided with cooling means.
Such a high-pressure discharge lamp is known from EP 0 315 261. By ceramic material is meant a refractory material such as monocrystalline metal oxides, for example sapphire, polycrystalline metal oxides, for example translucent, gastight sintered aluminium oxide or yttrium oxide, or non-oxidic materials such as aluminium nitride. The filling of the discharge vessel may comprise metals such as mercury or sodium, or metal halides such as iodides of Na, Tl, In, Sc, and/or the rare earth metals.
The known lamp has cooling means consisting of a separate, radially extending moulded piece which is in mechanical contact with the discharge vessel. The cooling means contribute to the possibility of a higher load, and thus of a higher power dissipation. Lamp characteristics, such as luminous flux, color rendering, and/or color temperature can be improved thereby compared with a similar lamp without the said cooling means.
A drawback of the known lamp is that separate moulded pieces are to be manufactured, which renders the lamp construction more complicated. In addition, narrow tolerances are to be observed. On the one hand, there is the risk of heat transport from the discharge vessel to the surrounding being limited owing to the fact that the moulded piece is too large for the discharge vessel. On the other hand, rejects may occur because the moulded piece is too small for being assembled together with the discharge vessel, or it may induce inadmissible mechanical strain during lamp operation.